1. Field of the Invention
The present invention relates to a coloring compound having high brightness and excellent storage stability, and a recording material using it as a coloring material.
2. Related Background Art
With the change of life-style by the progress of technology, coloring matter has come to be used not only for dying materials such as fibers, plastics, and leather heretofore, but also in various industrial fields making good use of its property of recording or displaying information. In particular, with the rapid spread of personal computers in recent years, hard copy technology typified by ink-jet and electrophotography has been advanced for recording characters and image information outputted from the computers.
Ink-jet printing technology has come to progress, in image quality, up to exceeding a silver halide photograph. However, stability in images with time may yet be insufficient in some cases. A coloring material used for an ink-jet ink is a dye or pigment. Although the former can obtain high-resolution quality of image, it is inferior in storage stability. While the weather-fastness of the latter is relatively good, there is a problem that the color reproduction range is narrow and inferior to dye ink in respect of quality of image.
The fading of a coloring material is considered to be induced by light, humidity, and active gasses in the environment, such as ozone, and there is a demand for development of a novel coloring material having high weather fastness.
A method wherein an ultraviolet absorbent, light stabilizer, antioxidant, or the like is used as an additive in an ink is made public as means for improving the weather fastness of an ink-jet ink (see Japanese Patent Application Laid-Open Nos. H11-170686, 2002-317135 and 2002-348512). Also, a technique as to a method for improving weather fastness by improving paper that is a recording medium is made public (see Japanese Patent Application Laid-Open Nos. 2002-19273, 2002-212237, 2002-219857 and 2003-48369). In any technique, the improvement in weather fastness is observed. However, in some cases, its effect may not be said to be sufficient. It is also attempted to improve the weather resistance of a dye molecule itself (see, for example, Japanese Patent Application Laid-Open Nos. 2000-303009, 2002-249677 and 2003-34758 for cyan-dyes, Japanese Patent Application Laid-Open No. 2002-302622 for magenta dyes, and Japanese Patent Application Laid-Open No. 2002-285022 for yellow dyes).
On the other hand, as properties required of a coloring material for a developer for electrophotography, i.e., a toner, there are mentioned absorption characteristics that can obtain a wide color reproduction range, optical transparency on an OHP sheet, and environmental stability. A toner made from a pigment as a coloring material is usually poor in transparency due to contribution of light scattering by coherent pigment particles, though it is excellent in stability of color tone with time. Toners using a dye as a coloring material are made public (see Japanese Patent Application Laid-Open Nos. H3-276161, H7-209912 and H8-123085). These toners may not be good in weather fastness in some cases, though they are good in transparency.
As described above, various proposals have been made. However, any coloring material having good hue and brightness as well as sufficient weather fastness may not yet be obtained in many cases.